The present invention relates to a processing system for processing a substrate using a solution and thermally processing it.
In a photoresist processing step of a semiconductor manufacturing process, resist solution is first coated on a surface of a substrate, such as a semiconductor wafer (hereinafter referred to as a wafer), thereby forming a resist film, the wafer is exposed with a predetermined pattern and thereafter subjected to development processing by use of a developer solution. Conventionally, a coating/developing system has been used to perform the aforementioned series of processes.
In general, the coating/developing system has a plurality of processing units. The processing units include, for example, an adhesion processing unit for improving the adhesion of resist to the wafer, a coating unit for coating the wafer with the resist solution, a thermal processing unit for subjecting the wafer coated with the resist solution to an atmosphere of a predetermined temperature to harden the resist, a thermal processing unit for subjecting the exposed wafer to an atmosphere of a predetermined temperature, and a developer unit for developing the exposed wafer with a developer solution. The wafer is transferred between these units by a transfer unit, such as a transfer arm. The wafer, on which a resist film has been formed in the coating unit and the thermal processing unit, is processed by an exposure processing unit, such as a step type projection exposure machine (hereinafter referred to as a stepper), so that it can be exposed with a predetermined pattern.
The aforementioned processing, e.g., the coating, developing and exposure processing, must be performed in a clean atmosphere. Therefore, it is necessary to avoid contamination of the wafer as far as possible. For this purpose, the coating/developing system and the exposure machine (e.g., the stepper) are encased by suitable casing members. Further, downflow of clean air is formed in the casings. The coating/developing system and the exposure machine (e.g., the stepper) are connected airtightly to each other. With this structure, the wafer can be transferred between the coating/developing system and the exposure machine in a clean atmosphere.
The coating/developing system, as described above, includes a coating unit for coating the wafer with the resist solution and a thermal processing unit for adjusting the temperature. There is a possibility that these units generate steam of an organic solvent, a high-temperature atmosphere, particles, etc. In addition, the internal pressures of the coating/developing system and the exposure machine are independent of each other, and not adjusted relative to each other.
When the coating/developing system is connected to the exposure machine, if the internal pressure of the coating/developing system is higher than that of the exposure machine, air flows from the coating/developing system to the exposure machine. Due to the airflow, the stream of an organic solvent, a high-temperature atmosphere and particles generated in the coating/developing system may flow into the exposure machine. Since the exposure machine (e.g., a stepper) requires very accurate alignment and an atmosphere of high cleanliness, an atmosphere from the outside of the exposure machine, in particular, a high-temperature atmosphere, stream of an organic solvent and particles, must be prevented from flowing into the exposure machine.